@graphit0 Yes I've explored them. But only Hack MD has a free web version with persistent notes storage. CodiMD & HedgeDoc work only on-premise, in local environment == not global.
That's why I chose HMD. To share links globally
BTW: talking about your feature request: I'm currently trying to run CodiMD or HedgeDoc locally with Docker Compose to check my plugin compatibility. But they don't want to connect to the DB 
Maybe someone could help me with running those apps in Docker?